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Title: Electronic Structure of the Hydroxo and Methoxo Oxometalate Anions MO3(OH)- and MO3(OCH3)- (M=Cr, Mo, and W)

Abstract

The electronic structure of the mononuclear hydroxo MO3(OH)- and methoxo MO3(OCH3)- Group 6 oxometalate anions (M ) Cr, Mo, and W) were examined by photodetachment photoelectron spectroscopy and electronic structure calculations at the density functional and CCSD(T) levels of theory. All of the anions exhibited high electron binding energies (>4.9 eV), with the lowest-energy detachment features arising from oxygen 2p-based orbitals. The combined experimental and theoretical results allowed the change in molecular orbital energy levels to be investigated as a function of metal (Cr, Mo, or W) and ligand (-OH, -OCH3). A number of fundamental thermodynamic properties of the anions and corresponding neutrals were predicted on the basis of the theoretical calculations. The calculations indicate high O-H bond dissociation energies for MO2(OR)(O-H) (R ) H, CH3) and MO3(O-H), consistent with their high Brønsted acidities (just below that of H2SO4 in the gas phase) and the high ionization energies of their conjugate base anions. This suggests that the corresponding radicals should readily abstract H atoms from organic molecules.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
877005
Report Number(s):
PNNL-SA-48098
Journal ID: ISSN 1089-5639; JPCAFH; 3565; 3568; KC0301020; TRN: US200608%%240
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 109(51):11771-11780; Journal Volume: 109; Journal Issue: 51
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ELECTRONIC STRUCTURE; ENERGY LEVELS; DENSITY FUNCTIONAL METHOD; PHOTOELECTRON SPECTROSCOPY; THERMODYNAMIC PROPERTIES; CHROMIUM COMPLEXES; MOLYBDENUM COMPLEXES; TUNGSTEN COMPLEXES; Environmental Molecular Sciences Laboratory

Citation Formats

Waters, Tom, Wang, Xue B., Li, Shenggang, Kiran, Boggavarapu, Dixon, David A., and Wang, Lai S. Electronic Structure of the Hydroxo and Methoxo Oxometalate Anions MO3(OH)- and MO3(OCH3)- (M=Cr, Mo, and W). United States: N. p., 2005. Web. doi:10.1021/jp054666x.
Waters, Tom, Wang, Xue B., Li, Shenggang, Kiran, Boggavarapu, Dixon, David A., & Wang, Lai S. Electronic Structure of the Hydroxo and Methoxo Oxometalate Anions MO3(OH)- and MO3(OCH3)- (M=Cr, Mo, and W). United States. doi:10.1021/jp054666x.
Waters, Tom, Wang, Xue B., Li, Shenggang, Kiran, Boggavarapu, Dixon, David A., and Wang, Lai S. Thu . "Electronic Structure of the Hydroxo and Methoxo Oxometalate Anions MO3(OH)- and MO3(OCH3)- (M=Cr, Mo, and W)". United States. doi:10.1021/jp054666x.
@article{osti_877005,
title = {Electronic Structure of the Hydroxo and Methoxo Oxometalate Anions MO3(OH)- and MO3(OCH3)- (M=Cr, Mo, and W)},
author = {Waters, Tom and Wang, Xue B. and Li, Shenggang and Kiran, Boggavarapu and Dixon, David A. and Wang, Lai S.},
abstractNote = {The electronic structure of the mononuclear hydroxo MO3(OH)- and methoxo MO3(OCH3)- Group 6 oxometalate anions (M ) Cr, Mo, and W) were examined by photodetachment photoelectron spectroscopy and electronic structure calculations at the density functional and CCSD(T) levels of theory. All of the anions exhibited high electron binding energies (>4.9 eV), with the lowest-energy detachment features arising from oxygen 2p-based orbitals. The combined experimental and theoretical results allowed the change in molecular orbital energy levels to be investigated as a function of metal (Cr, Mo, or W) and ligand (-OH, -OCH3). A number of fundamental thermodynamic properties of the anions and corresponding neutrals were predicted on the basis of the theoretical calculations. The calculations indicate high O-H bond dissociation energies for MO2(OR)(O-H) (R ) H, CH3) and MO3(O-H), consistent with their high Brønsted acidities (just below that of H2SO4 in the gas phase) and the high ionization energies of their conjugate base anions. This suggests that the corresponding radicals should readily abstract H atoms from organic molecules.},
doi = {10.1021/jp054666x},
journal = {Journal of Physical Chemistry A, 109(51):11771-11780},
number = 51,
volume = 109,
place = {United States},
year = {Thu Dec 29 00:00:00 EST 2005},
month = {Thu Dec 29 00:00:00 EST 2005}
}
  • The closo-[1-M(CO)3(h4-E9)]4- (E= Sn, Pb; M= Mo, W) anions have been obtained by extracting the binary alloys, KSn2.05 and KPb2.26, in ethylenediamine (en) in the presence of 2,2,2-crypt or in liquid NH3 followed by reaction with M(CO)3?mes (M= Mo, W) or Cr(CO)3.tol and in en or liquid NH3 solution. Crystallization of the molybdenum and tungsten salts was induced by vapor diffusion of tetrahydrofuran into the en solutions. The salts,[2,2,2-crypt-K]4[1-M(CO)3(h4-Sn9)]?en (M= Mo, W) crystallize in the triclinic system, space group P , Z= 4, a= 16.187(3)?, b= 25.832(4)?, c= 29.855(5)?, a= 111.46(1)o, b= 102.84(2)o, g= 92.87(2)o at -95 C (M= Mo)more » and a= 17.018(3)?, b= 27.057(5)?, c= 28.298(6)?, a= 66.42(3)o, b= 76.72(3)o, g= 87.27(3)o at 20 C (M= W). The salts, (CO)3M(en)2[2,2,2-crypt-K]4[1-M(CO)3(h4-Pb9)]? 2.5en (M= Mo, W) crystallize in the triclinic system, space group P , Z= 2, a= 16.319(3)?, b= 17.078(3)?, c= 24.827(5)?, a= 71.82(3)o, b= 83.01(3)o, g= 81.73(3)o at -133 C (M= Mo) and a= 16.283(4)?, b= 17.094(3)?, c= 24.872(6)?, a= 71.62(2)o, b= 82.91(2)o, g= 81.35(2)o at -153 C (M= W). The[1-M(CO)3(h4-Sn9)]4- anions were also characterized in liquid NH3 solution by 119Sn, 117Sn and 95Mo NMR spectroscopy. Unlike their fluxional precursor, nido-Sn94-, NMR studies show that the[1-M(CO)3(h4-Sn9)]4- anions are rigid on the NMR time scale. All possible inter- and intraenvironmental couplings, J(119,117Sn-119,117Sn), and J(119,117Sn-183W) and one J(119,117Sn-95Mo) coupling, have been observed and assigned. Complete spin-spin coupling constant assignments were achieved by detailed analyses and simulations of all spin multiplets that comprise the 119Sn and 117Sn NMR spectra and that arise from natural abundance tin isotopomer distributions and from natural abundance 183W, in the case of[1-W(CO)3(h4-Sn9)]4-.« less
  • We produced both doubly and singly charged Group VIB dimetalate species-M2O7 2-, MM'O72-, and M2O7 - (M, M'=) Cr, Mo, W)susing two different experimental techniques (electrospray ionization for the doubly charged anions and laser vaporization for the singly charged anions) and investigated their electronic and geometric structures using photoelectron spectroscopy and density functional calculations. Distinct changes in the electronic and geometric structures were observed as a function of the metal and charge state. The electron binding energies of the heteronuclear dianions MM'O7 2- were observed to be roughly the average of those of their homonuclear counterparts (M2O7 2- and M'2O7more » 2-). Density functional calculations indicated that W2O7 2-, W2O7-, and W2O7 possess different ground-state structures: the dianion is highly symmetric (D3d,1A1g) with a single bridging oxo ligand, the monoanion is a doublet (C1, 2A) with two bridging oxo ligands and a radical terminal oxo ligand, whereas the neutral is a singlet (C1, 1A) with two bridging oxo ligands and a terminal peroxo ligand. The combined experimental and theoretical study provides insights into the evolution of geometric and electronic structures as a function of charge state. The clusters identified might provide insights into the possible structures of reactive species present in early transition-metal oxide catalysts that are relevant to their reactivity and catalytic function.« less
  • Oxides of molybdenum and tungsten are an important class of catalytic materials with applications ranging from isomerization of alkanes and alkenes, partial oxidation of alcohols, selective reduction of nitric oxide and metathesis of alkeness.[1-10] While many studies have focused on the structure - function relationships, the nature of high catalytic activity is still being extensively investigated. There is a general agreement that the activity of supported MOx (M = W, Mo) catalysts is correlated with the presence of acidic sites, where the catalytic activity is strongly affected by the type of oxide support, delocalization of electron density, structures of tungstenmore » oxide domains and presence of protons« less
  • The reactions of deuterated methanol, ethanol, 1-propanol, 1-butanol, 2-propanol, 2-butanol and t-butanol over cyclic (MO3)3 (M = Mo, W) clusters were studied experimentally with temperature programmed desorption (TPD) and theoretically with coupled cluster CCSD(T) theory and density functional theory. The reactions of two alcohols per M3O9 cluster are required to provide agreement with experiment for D2O release, dehydrogenation and dehydration. The reaction begins with the elimination of water by proton transfers and forms an intermediate dialkoxy species which can undergo further reaction. Dehydration proceeds by a β hydrogen transfer to a terminal M=O. Dehydrogenation takes place via an α hydrogenmore » transfer to an adjacent MoVI = O atom or a WVI metal center with redox involved for M = Mo and no redox for M = W. The two channels have comparable activation energies. H/D exchange to produce alcohols can take place after olefin is released or via the dialkoxy species depending on the alcohol and the cluster. The Lewis acidity of the metal center with WVI being larger than MoVI results in the increased reactivity of W3O9 over Mo3O9 for dehydrogenation and dehydration.« less
  • A series of complexes (Et/sub 4/N)(M(CO)/sub 5/SR) (M = Cr, Mo, W; R = H, Ph), have been synthesized and characterized by /sup 1/H and /sup 13/C NMR and ir spectroscopies. Gentle heating causes these complexes to lose a carbonyl ligand, yielding the doubly bridged sulfur dimers M/sub 2/(CO)/sub 8/(..mu..-SR)/sub 2//sup 2 -/. The x-ray crystal structure of (Et/sub 4/N)/sub 2/(W/sub 2/(CO)/sub 8/(SPh)/sub 2/) has been determined. The complex crystallizes in the triclinic space group P /anti 1/ with unit cell parameters a = 9.8664 (17) /angstrom/, b = 9.8566 (22) /angstrom/, c = 11.8270 (26) /angstrom/, ..cap alpha.. =more » 65.790 (16)/degrees/, ..beta.. = 81.710 (16)/degrees/, ..gamma.. = 82.000 (16)/degrees/, V = 1034.0 (4) /angstrom//sup 3/, and Z = 1. Both mono- and dinuclear metal complexes readily react with phosphorus donor ligands to afford the carbon monoxide substituted complexes cis-M(CO)/sub 4/(P)(SR)/sup -/ (P = PMe/sub 3/, P(OMe)/sub 3/, PPh/sub 3/). In addition, the dimers react with 1 atm of carbon monoxide to re-form the mononuclear species M(CO)/sub 5/SR/sup -/ in quantitative yields. Unsuccessful attempts to insert CO/sub 2/, COS, or CS/sub 2/ into the M-SR bond in the M(CO)/sub 5/SR/sup -/ derivatives are noted. 25 references, 3 figures, 15 tables.« less